This review describes the important role and significance of cytochrome P450 monooxygenases in the metabolism, detoxification and selectivity of a broad spectrum of herbicides used for weed control in wheat and other cereals. Recent research on the isolation, characterization and reconstitution of induced microsomal cytochrome P450 monooxygenases directly responsible for herbicide oxidation, selectivity and resistance in wheat is emphasized. Reported evidence for the selection of similar wheat-like cytochrome P450 monooxygenases in the evolution of metabolism-based herbicide resistance in grassy weed populations is also presented.